RoundCube Webmail is a browser-based multilingual IMAP client with an
application-like user interface. It provides full functionality you
expect from an e-mail client, including MIME support, address book,
folder manipulation, message searching and spell checking.
RoundCube Webmail is written in PHP and requires a database: MariaDB,
PostgreSQL and SQLite are known to work.
The user interface is fully skinnable using XHTML and CSS 2.